jsp简单实现统计在线人数

//session操作类
public class SessionMap {

private static Map<String,HttpSession> sesMap = new ConcurrentHashMap<String,HttpSession>();

private SessionMap(){

}

private static class MapUtilsN{
private static SessionMap sessionMap = new SessionMap();
}

public static SessionMap getInstance(){
return MapUtilsN.sessionMap;
}

public void addMap(String sessionId,HttpSession session){
if(!sesMap.containsKey(sessionId)){
sesMap.put(sessionId, session);
}
}

public void removeMap(String sessionId){
sesMap.remove(sessionId);
}

public int getSize(){
return sesMap.size();
}

public HttpSession getSession(String key){
return sesMap.get(key);
}
}

//监听session创建及销毁
public class MySessionListner implements HttpSessionListener{

public void sessionCreated(HttpSessionEvent arg0) {
SessionMap.getInstance().addMap(arg0.getSession().getId(), arg0.getSession());
}

public void sessionDestroyed(HttpSessionEvent arg0) {
SessionMap.getInstance().removeMap(arg0.getSession().getId());
}

}

//web.xml中配置监听器
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> <welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<!-- 配置监听器 -->
<listener>
<listener-class>
practice.listner.MySessionListner
</listener-class>
</listener>
<!-- 设置session超时时间 -->
<session-config>
<session-timeout>10</session-timeout>
</session-config>
</web-app>